1. 获取 url

来源：https://stackoverflow.com/questions/20000911/get-complete-url-using-nginx-and-lua-with-openresty

ngx.var.request_uri # 只是 url 的 path

ngx.var.host .. '/' .. ngx.var.uri # 

ngx.var.scheme

ngx.var.query_string

2. 获取 body 数据

来源：https://openresty-reference.readthedocs.io/en/latest/Lua_Nginx_API/#ngxreqread_body

2.1 ngx.var.request_body

在获取body 数据之前，需要先调用函数 ngx.req.read_body()，否则获取到的 body 数据是空的。

ngx.req.read_body()
local body = ngx.var.request_body

2.2 ngx.req.get_body_data

Note that calling this function instead of using ngx.var.request_body or ngx.var.echo_request_body is more efficient because it can save one dynamic memory allocation and one data copy.